Air-guiding devices of a motor vehicle have at least one air-guiding element. A fundamental distinction is made here between air-guiding devices with fixed air-guiding elements and air-guiding devices with air-guiding elements which are shiftable between an extended operating position and a retracted inoperative position.
DE 30 19 150 A1, which is incorporated by reference herein, and DE 43 05 090 A1, which is incorporated by reference herein, both disclose an air-guiding device for a vehicle, which is arranged in a top rear region of the vehicle and comprises an air-guiding element which is shiftable from a retracted inoperative position, in which said air-guiding element is integrated in a surface-flush manner into the shape profile of the rear region, into an extended operating position, and conversely from the operating position into the inoperative position. The air-guiding element is designed as a supporting wing which is shiftable or transferable by means of an actuating device from the inoperative position into the operating position and vice versa. With said air-guiding devices, the coefficient of rear-axle downforce can be increased while the coefficient of drag remains the same or else is reduced.
U.S. Pat. No. 7,175,229 B2, which is incorporated by reference herein, discloses an air-guiding device of a motor vehicle with a fixed air-guiding element, wherein said fixed air-guiding element is assigned a propeller which is driven by the relative wind as the vehicle is moving.